Some Special Considerations

NASA officials used only a dozen words to list the primary objectives of
Apollo 11: "1. Perform a manned lunar landing and return. 2.
Perform selenological inspection and sampling."2 They had worked many years to be able to write
these objectives for a mission rather than a program. Ever since Apollo
was named in 1960, groups scattered throughout the country had studied
and planned the segments of that mission. Through 1965, this planning
had helped design the hardware. After that, with the exception of rework
caused by the fire in 1967, the mission planners had analyzed the
spacecraft capabilities and used this information to draft the most
minute details of the flight plan, which appeared in "final"
form on 1 July 1969, to be followed by "revision A" seven days
later.3

Chris Kraft's flight operations team in Houston designed and evaluated
most of the mission techniques. When the lunar landing flight became the
letter "G" on the chart of the progressive steps to land the
first men on the moon, Rodney G. Rose had already presided over 21
monthly meetings on how the crew would operate when it reached its goal.
The Rose team held 20 more meetings before being satisfied that it had
done all it could to smooth operations for what turned out to be Apollo
11. The 41st and final (summing-up) session was held in April 1969,
after a flight operations plan had been issued to outline in detail the
duties and actions to be performed at precise times.4

Rose's group served two specific purposes. First, its members were
observers, acquiring and passing on information about the spacecraft,
about flight crew operational procedures tried and either adopted or
rejected, and about engineering and development progress in qualifying
the suit and backpack for the lunar walk. The committee was, second, a
forum before which the mission planning and analysis team could air
computer-checked trajectories and techniques that affected the
interactions of hardware, crew, and fuel. Mission planners relied not
only on theoretical plans run through the computers, but also on actual
experience. Apollo 8, for example, needed only 2 periods of
onboard navigation during translunar and transearth coasting, rather
than the 10 previously planned. But past experience was set aside in one
case. As far back as Mercury, the crews had dumped any remaining fuel
before landing, as a safety precaution. What should be done about the
propellants in the lander's descent and ascent propulsion systems?
Should one be burned to depletion before lunar touchdown and the other
before redocking with the command module? The Apollo office objected to
this. It would be safer for the lunar module pilots to land as soon as
they reached the selected site than to cruise around burning up fuel,
with the possibility that they might have to touch down in an
undesirable site as a result. And it would be much better to go ahead
and dock than to fly around until they were low on fuel and then find,
if an emergency arose, that they had no way to return to the command
module. Firing to depletion in either case would be a last-ditch action
to ensure crew safety.5

Rose's team also helped Donald Slayton's support personnel decide how
many lunar revolutions should be flown before undocking and descent, to
make sure a well-rested crew would land on the moon with the sun angle
at 6 to 20 degrees, for the best lighting. Apollo 10
supplied the answer to this question. But the planners and trajectory
plotters could not set a specific flight path in concrete. With the
possibility that delays could cause them to miss a launch window
(determined by the moon's position in relation to the earth), they had
to plan for one mission in July, for another in August, and for a third
in September.6

Closely allied with Rose's work were the activities of Bill Tindall.
Long an associate of John Mayer in mission planning, Tindall had guided
Gemini efforts while Mayer had concentrated on early phases of Apollo
planning. When Gemini ended in 1966, Tindall had jumped in to help out
on the complex Apollo task, first as Mayer's deputy and then as data
coordination chief in the Apollo office. After 16 January 1968, the day
he assumed his new duties, his barrage of "Tindallgrams"
continued to enliven interoffice mails. Although he was now the liaison
between spacecraft and operations people, Tindall had been and still was
a mover of information and an assigner of tasks to specialists, either
to devise or to solve some mission technique. His memoranda, sometimes
addressed to hundreds of persons, often contained admonitions to one,
such as, "Bob Ernull please take note."7

Three areas of the mission demanded the toughest scouting by Tindall,
Rose, and other mission planners: descent, surface operations, and
ascent. Judged by the sheer weight of paperwork, descent seemed to be
the engineers' chief worry. Yet nobody wanted to set mission rules so
narrow that the crew could not land. Tindall and astronaut Harrison
Schmitt even discussed whether it was absolutely necessary for the
pilots to see exact landmarks. A touchdown outside the targeted area
might be quite satisfactory. They decided to leave the pilots some
options: "quit and come home, go another revolution and try again,
or don't worry about it and press on with the landing."8

Much of the concern about hitting a precise spot stemmed from
uncertainties about trajectory dispersions caused by the moon's strange
gravity fields. As more information was gathered about the mass
concentrations, called mascons, the Landing Analysis Branch fed the data
into computers for run after run (205 on just one study), trying to
evaluate fuel use and the probability of mission success based on
varying degrees of mascon influence on the descent trajectory. Tindall's
group also found guidance system faults that might result in unwanted
excursions. Flight controllers would have to help the crew decide
whether to go on or return to the command module. But returning to the
mother ship would be tricky, Tindall said. Dispersions had to be
severely contained to prevent the crew from flying a "dead
man" curve - an aimless trip across the lunar sky far out of range
of the command module's rescue capability.9

Constantly looking for clear explanations of how to guide a spacecraft
safely down to the moon, Tindall pounced on a lucid description by
George W. Cherry of the Massachusetts Institute of Technology and
arranged to have it reproduced and distributed to flight controllers,
managers, and astronauts. Cherry numbered each step of the descent phase
and outlined the guidance in finite detail, including how the spacecraft
should react and what the pilots should do. Cherry said that, during
"program 63 (P63)" (braking), the crew should steer out any
errors in attitude. During P64, as the lander tipped over to give the
crew a first look at the landing site, the thrusters that turned and
tilted the spacecraft should be carefully checked to make sure they were
working properly for the landing. From there to touchdown - P65, 66, and
67 - a maze of procedures would take the pilots through this most
critical step in the mission.10

When the Sea of Tranquility appeared the possible target for Apollo 11,
Tindall alerted planners to some unusual conditions in that location.
Although the lunar module would begin its descent from an orbital
station 18,300 meters above the mean surface of the moon, its altitude
above the landing zone would be much less than that. Tranquility, he
said, was 2,700 meters above the mean average, and even more in its
hilly area. So the landing approach would start low. Moreover, it would
be uphill because there was a one percent upward grade in the direction
of the flight path. These numbers, too, were fed into the computers to
check the crew's responses as they flew the trajectories in the lunar
module simulator. All through June and early July, memoranda and notes
about descent-propellant margins, use of the guidance system, and even
the views to be seen out the windows - continued to flow.11

In March 1969, Tindall had reminded his colleagues that the "lunar
surface stuff [was] still incomplete." Even the proper terminology
had not been decided. For example, Tindall said, the past practice of
continuing or aborting a mission by making a "go/no go"
decision seemed inappropriate; once the lander had settled on the lunar
surface, this might confuse the pilots. Tindall suggested something like
"stay/no stay," and that phrase became standard.12

There were other lunar surface worries. Suppose the vehicle landed at an
angle? That possibility did not worry the planners very much, because
the LM was designed to take off with as much as a 30-degree list, but
the guidance system did not know that. In flight, the attitude thrusters
fired automatically to keep the lander on an even keel, and they would
do the same thing on the ground. But nobody wanted these engines to fire
while on the lunar surface. George Cherry had the answer. "Just
joggling the handcontroller will not necessarily . . . stop the
firing," he said; the crew would have to cycle the guidance
switches to off and then to attitude hold to prevent the thrusters from
doing their programmed job.

The two hours after landing were critical. The pilots - who would act as
their own launch crew - had to go through a countdown after landing to
be prepared to leave the moon in a hurry if anything went wrong. They
would do the same thing the last two hours before their scheduled
departure. One crucial task in both these exercises was aligning the
guidance system's inertial platform. Most mission planners agreed that
the moon's gravity could be used for this reading, but Tindall worried
that the lander might be so near "one of those big damn lumps of
gold" that the alignment might be wrong and the lander might take
off on an incorrect course. Two days before launch, however, he reported
that "the various far-flung experts predict that mascons should
have no significant effect."13

Ascent from the moon also raised questions about trajectory dispersions.
Fairly small deviations could cause the lunar module to crash back into
the moon or miss the rendezvous with the command module. That was not as
big a worry, however, as the possibility of a failure in the guidance
system. The chances of the crew's taking off in the lunar module and
finding the command module would be extremely poor if all the guidance
equip ment failed.* Planners had
been studying manual takeover and steering of the lander even before
Grumman was selected to build the machine in 1962; in 1969 the computers
were still grinding away, trying to find a satisfactory solution. The
consensus appeared to be that controlling the lunar module manually was
only slightly better than doing nothing.

And a launch from the moon had to be exactly on time. If the crew fell
behind in the schedule, it would have to delay the launch until the
command module circled the moon again. It was also important that the
command module's path be precisely in line with the lunar module's
ascent trajectory (that is, "in plane"). The command module
pilot was responsible for tasks such as altering the command ship's
flight path - not just watching from his window. He would participate
actively by keeping a close eye on the lunar spacecraft while it was on
the surface and by being ready to help deal with whatever contingencies
the lander might encounter. To be prepared for any abort situation, the
command module pilot had a "cookbook" of 18 different two-page
checklists to cover all envisioned rescue operations.14

Landing, surface work, and ascent were going to be difficult, complex,
and demanding tasks. George Mueller, the manned space flight chief in
Washington, had therefore urged in mid-1968 that the first lunar landing
crew be selected as soon as possible.15

* Mission planner Carl Huss had
talked with the astronauts (especially Russell Schweickart) during the
early days about manual control. At that time, however, his group
thought the lander had enough redundancy and backup systems to do the
job. As the landing flight drew near, astronaut interest in manual
control naturally heightened.